1. Field of the Invention:
The present invention relates to a binocular tube for microscopes, and more particularly it pertains to a binocular tube which can be adjusted of its angle of inclination for being suitable as a binocular tube for microscopes to be used in surgical operations.
2. Description of the Prior Art:
In a stereo-microscope, and especially in a microscope for surgical operations, the microscope per se is used to perform a surgical operation while observing the lesion of the patient. Therefore, in case an objective lens has a long focal distance, it is desired that the distance from the eye-point of the ocular lens up to the work surface be as short as possible, and also that the angle of inclination of the ocular tube can be adjusted or varied at will.
As such a tube whose angle of inclination can be varied, there is the one disclosed in, for example, Japanese Patent Preliminary Publication No. Sho 53-70838. This prior art tube will be described by giving reference to FIGS. 1 and 2. In FIG. 1, reference numeral 1 represents a stationary tube unit for holding a focusing lens 2, and this stationary tube unit is fixed to the microscope body M via a mount 1a. Numeral 3 represents a movable tube unit which is fitted in the stationary tube unit 1 for rotation in the directions of arrows A. Numeral 4 denotes a pair (but one of the pair is illustrated) of ocular tube units each holding an ocular lens not shown. This ocular tube unit 4 is fitted in the movable tube unit 3 for rotation in the directions shown by the arrows B for the purpose of adjusting the interval between the eyes and for causing adaptation to the selected direction of observation. Numeral 5 is a rotary mirror which is rotatably secured by an axis to the stationary tube unit 1 and coupled to the movable tube unit 3 via a transmission means 6. Numeral 7 represents a pair (but only one of the pair is illustrated) of 45.degree. Dach prims disposed within the movable tube unit 3, and a relay lens 8 is secured to that surface of this prism which faces the rotary mirror 5 side. Numeral 9 denotes a pair (but only one of the pair is illustrated) of deflector mirrors disposed within the movable tube unit 3 but they are independent of the transmission means 6. Numeral 10 represents a pair (but only one of the pair is illustrated) of diamond-shaped prisms disposed in the respective ocular tube units 4, one for each ocular tube unit. The above-mentioned units and members constitute an image transmission system, and also the image formed by the focusing lens (image lens) 2 is focused as a correct or erect image on an intermediate image surface 11 via the transmission system. It should be noted here that the transmission means 6 is so designed that, in case the optical axis of the movable tube unit 3 is changed for an angle .alpha. by altering the angle of inclination of the ocular tube unit 4, the rotary mirror is rotated through an angle of .alpha. /2. Also, the play of the transmission means 6 which is developed due to a permissible manufacturing error is absorbed by a spring 12.
Accordingly, by the use of this tube arrangement, it should be noted that, even when the angle of inclination of the ocular tube unit 4 is altered, it is possible to achieve a correct observation of an erect image.
However, in the above-stated conventional device, the arrangement thereof is such that the optical path extends in a direction in which the optical path simply departs away from the rotary mirror 5. Accordingly, the tube arrangement per se tends to assume a large size. Also, as shown in FIG. 2, in case the angle of inclination of the ocular tube unit 4 is altered, the radius R of rotation from the center of rotation up to the ocular lens increases. Especially, when the angle of inclination becomes 90.degree., i.e. when the incident light to the tube becomes parallel with the emitting light therefrom, the distance L between the mounting surface 1b of the tube to the microscope and the mounting surface 4a of the ocular lens increases, with the result that the distance from the sample surface (work surface) to the eye-point of the observer increases, hence the drawback that the operability in both observation and manipulation is aggravated.